BMW Differential and Gearing Upgrades

Upgrade your drivetrain performance with ECS Tuning Performance Polyurethane Differential Bushings—engineered specifically for BMW F8x/G8x models and designed to deliver superior power transfer, durability, and driving precision.

Factory rubber differential bushings are built for comfort, absorbing vibrations between the differential and chassis during everyday driving. However, they are a known wear item that degrade over time—especially under spirited or aggressive driving conditions. Many F8x/G8x owners experience premature cracking and wear, leading to excessive drivetrain movement, reduced throttle response, and unwanted wheel hop.

ECS Tuning’s in-house engineered polyurethane differential bushings provide a high-performance solution to these common issues. By significantly reducing drivetrain deflection, these upgraded bushings enhance throttle response, improve handling stability, and minimize wheel hop—resulting in a more connected and controlled driving experience.

Constructed from durable 95A durometer red polyurethane and paired with precision CNC-machined 6061-T6 aluminum sleeves, these bushings are built to withstand extreme driveline forces while maintaining street-friendly comfort. Unlike solid or delrin mounts, ECS polyurethane bushings strike the perfect balance between performance and daily drivability—delivering increased rigidity without excessive noise, vibration, or harshness (NVH).

Whether you're carving canyon roads, launching at the drag strip, or simply commuting, these performance differential bushings ensure more efficient power delivery from the differential to the wheels—giving you better throttle modulation, traction, and overall control.

Key Features & Benefits:

Performance polyurethane differential bushings for BMW F8X models
Reduces drivetrain movement and improves power transfer
Enhances throttle response and minimizes wheel hop
95A durometer polyurethane for optimal balance of performance and comfort
CNC-machined 6061-T6 aluminum inserts with Type II black anodizing for corrosion resistance
Resistant to oil, chemicals, ozone, and road salt for extended service life
Designed to handle high torque loads and extreme driving conditions
Engineered using real-world load data and worst-case operating scenarios
Maintains street-friendly NVH levels compared to solid mounts
Replace worn factory bushings with ECS Performance Polyurethane Differential Bushings and experience tighter handling, improved drivetrain response, and long-lasting reliability.

Worn rubber differential mounts will lead to the differential twisting and shifting around in the rear subframe. Not only will this be noisy but it's bad for driver confidence and bad for the chassis as well. Even on fresh rubber bushings the differential has deflection and twist, especially if the car has been modified for more torque. Since the differential is centrally mounted in the rear subframe, with all suspension mounts interconnected, a differential with too much deflection will affect handling and could even damage the rear subframe.

These 88A urethane E46 M3 diff mounts are much stiffer than stock but still not as solid as our Turner aluminum/Delrin bushings. This set will resist twisting much better than the stock rubber mounts. Included is the front diff mount and two rear mounts in the cover.

Revitalize your driving experience with ECS Tuning's In-House Engineered Performance Polyurethane Differential Bushings. Say goodbye to soft factory rubber bushings and their deflection. These innovative bushings provide a substantial improvement in the connection between your right foot, the chassis, and the wheels. The outcome is a crisper power transfer from the differential to the wheels, resulting in enhanced throttle control for various driving activities. Notably, these polyurethane bushings achieve these benefits without the harshness or vibration often linked to delrin or solid differential mounts.

Manufactured using a robust 88A durometer polyurethane and a black anodized 6061-T6 aluminum sleeve, these bushings offer superior resistance to chemicals, ozone degradation, road salt, and general wear and tear. This translates to an extended service life.

Urethane mounts keep the differential from twisting under load. As torque is put through the driveline it causes anything to twist and move. The differential is mounted to the subframe and the twisting and deflection can be transferred to the rest of the chassis. With a stiffer mount the differential will not deflect as much. This improves seat-of-the-pants feeling to the driver, giving more feedback for smoother power delivery. In theory, there's also more torque being sent to the drive wheels since it's not being used up shifting the diff weight around.

These are tough 88A durometer urethane bushings with a anodized almunum center sleeve, engineered by ECS. This is a set of E36 diff bushings - 1 for the front and 2 for the rear cover. New high-grade hardware is included (the front bolt has a tendency to snap from all that torque twisting!).

Hands down - one of the best performance upgrades you can make to an E46 M3, E60 M5 or E63/E64 M6! With almost no downside you can make your BMW much quicker by swapping in a new ring & pinion gear set. The gearing used to be overlooked when planning modifications but the 3.85, 3.91, and 4.10 gears are now one of our biggest selling upgrades for the E46 M3! With a rear end gear upgrade you get the effects of adding horsepower but without adding any more stress to the engine or drivetrain. It's one of the best areas to get return from your modification spending. Using a shorter (numerically higher) gear ratio will give you better acceleration. The R&P acts as a torque multiplier, putting the engine into the power band sooner for each gear. There is an 6% increase in torque at the wheels with the shorter R&P. Want to make your car faster off the line or out of corners? Or avoid a downshift to pass on the highway? This is what you need.

The R&P can be installed on its own but for cars that have more than 60,000 miles it would be a better idea to rebuild the whole diff. The factory viscous limited slip units have a typical lifespan of 50-70,000 miles. We offer diff rebuilding with 3.85 or other gear options and you get a fully-rebuilt and serviced limited slip unit at the same time. Click here for our diff rebuild options.

3.85 Gearing Example: 2004 M3, 6-speed manual, 275/35-19" rear tires

Gear RatioGearSpeedRPM

40 MPH in 4th
3.62 4th 40mph 2,250rpm
3.85 4th 40mph 2,350rpm

70 MPH Cruise
3.62 6th 70mph 2,650rpm
3.85 6th 70mph 2,800rpm

5th Gear Speed at Redline
3.62 5th 175mph 8,000rpm
3.85 5th 165mph 8,000rpm

Why 5th? Because 6th does not have the mechanical advantage to get past wind resistance at these speeds - it is more of a cruise/overdrive gear. Using 5th for comparison purposes is much more relevant than having to take into account wind direction, resistance, grade, elevation, tire sizing, etc. These numbers are for comparisons among gear ratios only, not to determine what your M3 will top out at.

This item is the genuine BMW part and the ring & pinion set only. You will need to have this professionally installed into your existing differential. BMW does not supply differential rebuild parts (bearings, shims, plates, etc.) so only a qualified shop that is experienced in BMW diff rebuilding should perform this installation. We also offer built differentials and exchanges, click here.

This item fits the following BMWs:
2001-2006 E46 BMW M3
2004-2010 E60 BMW M5
2004-2011 E63 BMW M6

OEM part number 33108311351

Often overlooked, scheduled rear differential service is very important. Over time gear lube breaks down causing bearings and internal components fail. Regular maintenance will keep your vehicle running properly for years to come.

Please see kit contents tab for included items.

This package of OEM E82 E90 E92 diff mounts replaces the stock rubber diff bushings. On a tuned 335i you may have noticed more driveline shudder or problems hooking up during hard launches. What happens is the stock rubber bushings are under constant flex as engine torque is transmitted through the differential. Under normal driving with a stock car the bushings are rarely stressed. But factor in significant additional torque from a tuned N54/N55 and the stock rubber will quickly show its weaknesses. You may have even broken a diff bolt or two as the heavy differential shifts around. Even non-turbo E82 and E9X models may benefit from fresh bushings.

This is a set of stock rubber bushings, made by OEM supplier Lemforder. They are the same as the Genuine BMW E9X diff mount bushings, but without the more expensive branding. If you're turned off by potential side effects of urethane or Delrin then the OEM diff mounts are your best option. The OEM mounts fit and perform just like the originals so there is no second guessing their quality. If you're looking for an upgrade we offer E9X solid Delrin and aluminum diff mounts that work well, even in street applications.

E9X Diff Mount Set includes:

• 33176760287 x 2, front differential mount
• 33176770866 x 1, rear differential mount
• (new hardware is optional and can be ordered separately below)
  
  This item fits the following BMWs:
  2008-2012 E82 BMW 128i 135i
  2006-2011 E90 BMW 325i 325xi 328i 328xi 328i xDrive 330i 330xi 335d 335i 335xi 335i xDrive - Sedan
  2006-2012 E91 BMW 325xi 328i 328xi 328i xDrive - Wagon
  2007-2013 E92 BMW 328i 328xi 328i xDrive 335i 335is 335xi 335i xDrive - Coupe
  2007-2013 E93 BMW 328i 335i - Convertible